US7138579B2

US7138579B2 - Flexible grounding strip

Info

Publication number: US7138579B2
Application number: US11/294,081
Authority: US
Inventors: George D. Megason; Thomas T. Hardt
Original assignee: Hewlett Packard Development Co LP
Current assignee: Hewlett Packard Development Co LP
Priority date: 2003-12-19
Filing date: 2005-12-05
Publication date: 2006-11-21
Anticipated expiration: 2023-12-19
Also published as: US6972369B2; US20050133236A1; US20060084302A1

Abstract

A flexible grounding strip includes an electrically conductive strip having an elongated base, opposite sides of which extend to respective flanges spaced from the base. Each flange extends from one side of the base and terminates at an edge generally facing the opposed side of the base. The edges are spaced from each other. Each of the opposite sides have lengthwise spaced slots extending partly across the base towards the opposite side of the base. The slots extending from one side of the base are interleaved with slots extending from the opposite side of the base.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of application Ser. No. 10/742,041, filed Dec. 19, 2003 now U.S. Pat. No. 6,972,369, which is hereby incorporated by reference herein.

BACKGROUND

Electromagnetic interference (EMI) can create operational problems in many types of electronic devices, including computer systems. Proper grounding of components in these devices is therefore desirable to minimize the effect of EMI. Grounding is accomplished by providing a pathway for conducting electricity from a component to a grounding object of greater size, such as the chassis of the electronic device. It is therefore desirable to ensure that an electrical connection is maintained at the maximum number of interfaces between a component and the grounding object.

The design of some components does not always ensure a proper electrical connection at a given interface. In these instances, it is desirable to have a separate grounding device that may provide an electrical connection at the interface. The likelihood of providing an electrical connection at an interface is increased if the grounding device is flexible and can conform to the surfaces of the components that are connected. It is also sometimes desirable to install or remove components of an electronic device after the device has been assembled. It is therefore desirable to have a grounding device that can be easily installed or removed from an electronic device without requiring disassembly of the electronic device.

SUMMARY

The problems noted above are solved in a large part by a flexible grounding strip comprising an electrically conductive strip having an elongated base, opposite sides of which extend to respective flanges spaced from the base. Each flange extends from one side of the base and terminates at an edge generally facing the opposed side of the base. The edges are spaced from each other. Each of the opposite sides have lengthwise spaced slots extending partly across the base towards the opposite side of the base. The slots extending from one side of the base are interleaved with slots extending from the opposite side of the base.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of embodiments, reference will now be made to the accompanying drawings in which:

FIG. 1 illustrates a front view of a flexible grounding strip in accordance with embodiments of the invention;

FIG. 2 illustrates a top view of the flexible grounding strip of FIG. 1;

FIG. 3 illustrates a front perspective view of the flexible grounding strip of FIG. 1;

FIG. 4 illustrates a perspective view of a flexible grounding strip being installed on a component in accordance with embodiments of the invention;

FIG. 5 illustrates a top sectional view of a flexible grounding strip installed on a rib in accordance with embodiments of the invention;

FIG. 6 illustrates a top view of a flexible grounding strip installed on a rib in accordance with embodiments of the invention;

FIG. 7 illustrates a perspective view of flexible grounding strips installed on an input/output backplane in a computer system in accordance with embodiments of the invention;

FIG. 8 illustrates a perspective view of flexible grounding strips installed on an input/output backplane in a computer system in accordance with embodiments of the invention;

FIG. 9 illustrates a detailed view of features that can be incorporated into an input/output backplane in accordance with embodiments of the invention;

FIG. 10 illustrates a front view of a flexible grounding strip in accordance with embodiments of the invention;

FIG. 11 illustrates a top view of a flexible grounding strip in accordance with embodiments of the invention; and

FIG. 12 illustrates a top view of a flexible grounding strip in accordance with embodiments of the invention.

DETAILED DESCRIPTION

Certain terms are used throughout the following description and claims to refer to particular system components. As one skilled in the art will appreciate, computer companies may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “electrical connection” (or variations thereof is intended to mean either an indirect or direct electrical connection. Thus, if a first device is electrically connected to a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections.

The following discussion is directed to various embodiments. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure. In addition, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure is limited to that embodiment.

Referring now to FIGS. 1–3, a flexible grounding strip 50 is shown in accordance with an embodiment of the invention. Flexible grounding strip 50 is an elongated, electrically conductive channel strip having base 55, sidewall 90, sidewall 100, flange 95, and flange 105. Flange 95 is spaced from base 55 and extends towards sidewall 100 and base 55. Similarly, flange 105 is spaced from base 55 and extends towards sidewall 90 and base 55.

Flexible grounding strip

50 has a series of lengthwise-spaced slots 60 arranged so that an individual slot extends through the thickness of the strip and widthwise across a

sidewall

90, 100. Slot 60 further extends into, and at least partly across, base 55 and terminates in a curved end 70. Slot 60 may also extend into

flanges

95 or 105. The dimensions and spacing of slots 60 impart flexibility to enable flexible grounding strip 50 to bend transversely of its length during installation and to maintain contact with adjacent components after installation.

Slots

60 can be arranged so that alternating slots begin at

opposite sidewalls

90 and 100. For example, slot 61 begins at sidewall 90, while slot 62 begins at sidewall 100 and slot 63 begins at sidewall 90. The alternating pattern is repeated throughout flexible grounding strip 50, with slots 60 extending across

sidewalls

90 and 100. This alternating pattern provides sufficient flexibility for grounding strip 50 while minimizing stress concentrations that could cause permanent deformation of the strip during installation.

Referring now to FIG. 4, a perspective view of a flexible grounding strip 51 is shown being installed on component 300. The slots 59 allow flexible grounding strip 51 to easily flex or bend transversely of its length during installation of flexible grounding strip 51 onto section, or rib, 310 of component 300. Flexible grounding strip 51 is installed from direction 57 that is generally perpendicular to rib 310, and flexes, or bends, in direction 58, to become parallel to rib 310.

Flexible grounding strips

52 and 53 are shown after installation onto component 300 has been completed. Thus, the dimensions and spacing of slots 59 enable flexible grounding strips 51–53 to bend transversely of their length and be easily installed on rib 310.

Referring now to FIGS. 5 and 6, a top sectional view is shown of flexible grounding strip 51 installed on rib 310. These views show details of rib 310, including

surfaces

305 and 306 connected by

edges

307 and 308. Flexible grounding strip 51 includes base 55 and

flanges

96 and 106. FIG. 5 shows

flanges

96 and 106 contacting surface 305 of rib 310.

Flanges

96 and 106 project toward base 55 such that the flanges will hold flexible grounding strip 51 in place on rib 310 without additional components being attached to the rib.

Flexible grounding strip

51 is constructed such that the distance between base 55 and the end of

flanges

96, 106 is less than the thickness of rib 310 (i.e., the length of edges 307, 308). Therefore, flange 96 deflects as flexible grounding strip 51 is installed on rib 310 and maintains contact with the rib once installed. This allows flange 96 to retain flexible grounding strip 51 in place on rib 310 without additional components being attached or disposed adjacent to rib 310.

When installed on rib 310, flange 106 also deflects to engage surface 305 and projects a distance 311 above the surface. Component 500, when installed adjacent to rib 310 at a distance 311 or closer, will contact flexible grounding strip 51. The flexibility and cross-sectional shape of flexible grounding strip 51 allow

flanges

96 and 106 to maintain contact with rib 310 whether or not component 500 is installed.

FIG. 6 shows additional component 400 disposed adjacent to, rib 310 such that there is a minimal gap, if any, between component 400 and rib 310; Flange 96 maintains contact with both component 400 and rib 310, while flange 106 maintains contact with both component 500 and rib 310. The flexibility of flexible grounding strip 51 helps to allow

flanges

96 and 106 to maintain contact with

components

400 and 500, respectively, when the components are installed at distance 311 or less. This contact is maintained despite the variation in distances between rib 310 and

components

400 and 500. Further, if component 500 is disposed next to rib 310 such that the distance between component 500 and rib 310 varies along the length of rib 310, the flexibility of flexible grounding strip 51 allows flange 106 to maintain contact with rib 310 and component 500.

For purposes of example,

components

400 and 500 are ungrounded components disposed adjacent to surface 305 of rib 310, which is grounded. Flexible grounding strip 51, rib 310, and

components

400 and 500 are comprised of electrically conductive materials. Flexible grounding strip 51 is in contact with

components

400 and 500 as well as rib 310 of component 300. Therefore, an electrical connection will be formed between grounded rib 310 and

ungrounded components

400 and 500, such that

components

400 and 500 will be properly grounded.

Referring now to FIGS. 7–9, flexible grounding strips 71, 72, and 73 have been installed on input/output (I/O) backplane 320 in computer system 330 with component 331 or other source of electromagnetic interference (EMI). For purposes of illustration,

slot blanks

340 and 350 are representative of any component 331 that is capable of being attached to I/O backplane 320. Component 331 may be a peripheral component interface board or other printed circuit board (not shown).

Slot blanks

340 and 350 are shown here for simplicity and clarity in illustration and may be used in conjunction with I/O backplane 320 when component 331 is not present in computer system 330.

Flexible grounding strips 71–73, comprising lengthwise-spaced slots 40 to impart flexibility, are installed onto I/O backplane 320.

Slot blanks

340 and 350 have been attached to I/O backplane 320 in such a manner that flexible grounding strips 71 and 72 are between, and in contact with, I/O backplane 320 and

slot blanks

340 and 350. EMI generated by computer system 330 or component 331 may escape from computer system 330 if I/O backplane 320 and component 331, or slot

blanks

340, 350, are not properly-grounded. Flexible grounding strips 71 and 72 will permit

slot blanks

340 and 350 to be properly grounded, in part due to slots 40 imparting flexibility to the flexible grounding strips 71 and 72. This flexibility provides proper grounded even if there are gaps of varying distances between I/O backplane 320 and

slot blanks

340 and 350.

As shown in FIG. 9, a notch.311 may be cut into rib 310 to make installation of the flexible grounding strips 71–73 easier. Notch 311 provides an area of reduced width for rib 310 and allows a flexible grounding strip 71–73 to be installed onto rib 310 by inserting an end into notch 311 and sliding it up rib 310 in the manner shown in FIG. 4. In addition, slot 312 may be cut in the base of I/O backplane 320 to engage

slot blanks

340 and 350 and control their position relative to the I/O backplane.

It should be noted that the flexible grounding strips 71–73 provide many benefits in grounding components such as I/O backplane 320 and any attached components, such as

slot blanks

340 and 350. The extreme flexibility of the flexible grounding strips 71–73 may allow the installation of flexible grounding strips 71–73 onto I/O backplane 320 shown in FIG. 7,without removal of the I/O backplane 320 from computer system 330. Further simplifying installation of the flexible grounding strips 71–73 is the fact that no tools are needed to install the flexible grounding strips 71–73 onto I/O backplane 320.

In addition, any separation of the flexible grounding strips 51–53 from I/O backplane 320 or attached components will be limited to a small region due to the flexibility of flexible grounding strips 71–73. The flexible nature of flexible grounding strips 71–73 allows them to conform to the surface on which they are installed, thereby increasing the opportunity for providing an effective electrical connection and grounding mechanism. It should also be noted from the included Figures that flexible grounding strips 71–73 contain no sharp or exposed edges that would be likely to injure an individual who places his or her hands in proximity to flexible grounding strips 71–73.

The flexibility of the grounding strips may be due to several factors, including, but not limited to the thickness and material properties of the strip material, the number and arrangement of the slots through the strip, and the configuration of the sidewalls and flanges. For example, FIG. 10 shows a flexible grounding strip 150 comprising a base 155 and two opposing

sidewalls

190 and 195. A series of lengthwise-spaced slots 160 are arranged so that an individual slot extends across either

sidewall

190 or 195 and into, and at least partly across, base 155. Slots 160 are arranged so that a part of center portion of base 155 does not have slots 160 extending across it but grounding strip 150 can bend transversely of its length.

The configuration of the sidewalls and flanges of a flexible grounding strip is also not limited. For example, in reference to FIG. 2, the angle between

flanges

95 and 105 and sidewalls 90 and 100 may be varied. Further, and in reference to FIG. 11, flexible grounding device 170 comprises a base 175 disposed between

curved portions

180 and 185 with

ends

181 and 186.

Curved portions

180 and 185 and ends 181 and 186 function similar to sidewalls 90 and 100 and

flanges

95 and 105 of the embodiment of FIG. 2.

Other embodiments of the invention may also incorporate only one sidewall and flange, as shown in FIG. 12. Flexible grounding device 240 comprises sidewall 242 disposed between base 241 and flange 243, which extends towards base 241. This one-flange embodiment may be utilized in situations where an embodiment with two sidewalls may not be used. For example, the outermost rib in an I/O backplane may have only one edge that is accessible. In addition, there may be situations where it is not possible to install a flexible grounding strip by sliding it along a rib, and in these instances, an embodiment with only one sidewall may be installed from the side of the rib and thereby provide effective grounding of adjacent components.

The embodiments described above may be produced by different methods of manufacturing. One such method uses a progressive die to perform the various steps needed to transform a strip of electrically conductive material into a flexible grounding strip. In this method, a strip of electrically conductive material is fed into the progressive die and transported across several stations. At each station, a separate die is used to perform a manufacturing step, such as removing or bending material. For example, the slots incorporated in the embodiments described above may be formed by stamping the strip of electrically conductive material with a die that produces the desired slot geometry. A separate die may be used to cut the strip into the desired external dimensions for the preferred flexible grounding strip. Finally, another die may be used to bend the material into the desired shape.

The above discussion is meant to be illustrative of the principles and various embodiments. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. For example, embodiments include alternative slot geometry and configurations from those described in the above discussion. It is intended that the following claims be interpreted to embrace all such variations and modifications.

Claims

1. A flexible grounding strip comprising:

an electrically conductive strip having an elongated base, opposite sides of which extend to respective flanges spaced from the base,

each flange extending from one side of the base and terminating at an edge generally facing the opposed side of the base; said edges spaced from each other;

each of said opposite sides having lengthwise spaced slots extending partly across the base towards the opposite side of the base, the slots extending from one side of the base are interleaved with slots extending from the opposite side of the base.

2. The flexible grounding strip of claim 1, wherein the slots terminate partly across the width of the base in curved ends.

3. The flexible grounding strip of claim 2, wherein the curved ends have a radius greater than the width of the slot.

4. The flexible grounding strip of claim 1, wherein each side comprises a curved portion between each side and its respective flange.

5. The flexible grounding strip of claim 4, wherein the lengthwise spaced slots extend through the curved portions.

6. The flexible grounding strip of claim 4, wherein the elongated base, curved portions, and flanges comprise a one-piece strip.

7. A flexible grounding strip comprising:

an electrically conductive strip having an elongated base with opposite sides; and

a plurality of lengthwise spaced slots extending from one side of the elongated base partly across the base towards the opposite side of the base, wherein the slots extending from one side are disposed between slots extending from the opposite side.

8. The flexible grounding strip of claim 7, wherein each side of said electrically conductive strip further comprises a flange spaced from the elongated base.

9. The flexible grounding strip of claim 8, wherein each side of said electrically conductive strip further comprises a curved portion between each side and its respective flange.

10. The flexible grounding strip of claim 9, wherein said plurality of lengthwise spaced slots extend through the curved portions.

11. The flexible grounding strip of claim 9, wherein the elongated base, curved portions, and flanges comprise a one-piece strip.

12. The flexible grounding strip of claim 7, wherein each of plurality of the slots terminate partly across the width of the base in curved ends.

13. The flexible grounding strip of claim 12, wherein the curved ends have a radius greater than the width of the slot.

14. A flexible grounding strip comprising:

an electrically conductive strip having an elongated base with opposite sides, wherein each side has a respective flange extending therefrom and spaced from the elongated base; and

a plurality of lengthwise spaced slots extending from one side of the elongated base partly across the base towards the opposite side of the base, wherein the plurality of lengthwise-spaced slots are arranged so that slots extending from one side alternate with the slots extending from the opposite side.

15. The flexible grounding strip of claim 14, wherein each side of said electrically conductive strip further comprises a curved portion between each side and its respective flange.

16. The flexible grounding strip of claim 15, wherein said plurality of lengthwise spaced slots extend through the curved portions.

17. The flexible grounding strip of claim 14, wherein the elongated base, curved portions, and flanges comprise a one-piece strip.

18. The flexible grounding strip of claim 14, wherein each of plurality of the slots terminate partly across the width of the base in curved ends.

19. The flexible grounding strip of claim 18, wherein the curved ends have a radius greater than the width of the slot.